1. Technical Field
The present disclosure relates to a gate drive circuit that drives a semiconductor switch.
2. Description of the Related Art
A gate drive circuit for a semiconductor switching element (also referred to simply as a switching element) applies a gate voltage to the gate terminal of the switching element to control its on and off states. This control may be referred to below simply as gate driving. The gate drive circuit controls the on and off states of a high-voltage switching element such as, for example, an insulated gate bipolar transistor (IGBT), which is a type of power device.
In a gate drive circuit for this type of power device, a reference voltage on the output side connected to the switching element is very high. Therefore, a direct-current component needs to be isolated between a primary side, into which a control signal is entered, and a secondary side, from which a gate voltage is output to the switching element. In other words, signal ground needs to be isolated.
An electric circuit element that can isolate the direct-current component between the primary side and secondary side may be referred to as a signal isolator. The signal isolator is essential to the driving of a power device. The signal isolator isolates logic ground and radio-frequency (RF) ground from each other.
To drive a switching element, which is a power device, an isolated power supply unit is required separately. The isolated power supply unit may cause a circuit size to be increased. If the gate drive circuit enables not only a gate signal but also a gate power to be isolatedly supplied to the gate of the switching element, an external isolated power supply unit becomes unnecessary, enabling the gate drive circuit to be made compact.
Japanese Unexamined Patent Application Publication No. 2008-067012 discloses an electric power transmission system, as illustrated in FIG. 1, in which an open-ring resonator is used as a signal isolator.